There is a difference how you change your language if you're using the Desktop or the iOS version, please read the instructions below.
When you login into your account at www.roomle.com, in the top right corner you can find the language icon. Please click on it and select the desired language.
Roomle uses the language that is set as default for your iPad or iPhone. Thus, you need to go to your device's Settings and then select 'General Settings'. Go to the Language & Region field and click on iPad/iPhone Language. Your Roomle App will automatically switch to the selected new language.